This disclosure relates to an outer engine case for a gas turbine engine and, more particularly, to a single-piece outer engine case that surrounds at least two modules or more that may include portions of a combustor section, turbine section and transition duct section.
An outer engine case for a gas turbine engine includes multiple case sections that are secured to each other at flange connections. The multiple case sections are required to facilitate installation of various internal gas turbine engine components such as a diffuser assembly, rotor assemblies, vane assemblies, combustors, seals, etc. For example, in one known configuration there is a combustor case, a high pressure turbine case, a transition-duct case and a low pressure turbine case. The combustor case is bolted to the high pressure turbine case at a first external flange joint, the high pressure turbine case is bolted to the transition-duct case at a second external flange joint, and the transition-duct case is bolted to the low pressure turbine case at a third external flange joint. Each external flange joint includes flanges that extend radially outwardly from an outer surface of the outer engine case.
The use of these multiple case sections and multiple flange joints is disadvantageous from cost, assembly, and weight perspectives. Further, each external bolted flange joint provides a potential leak path for the gas turbine engine. Leakage adversely affects the operating performance of the gas turbine engine.
Accordingly, there is a need to provide a lighter engine case design that reduces leakage, as well as addressing the other deficiencies in the prior art mentioned above.